• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.6
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• pp.214-224
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• 2008

Member force, strain and stress distribution of a section are obtained for optimized standard 25m~45m PSSC composite bridge subjected to dead and live load in order to interpret the effect of prestressing and deformation of tendon. The stress and strain distribution and moment capacity are obtained for both noncomposite and composite section and for allowable stress limit state, yield limit state and strength limit state. Reliability analysis is conducted after assuming limit states for stress and flexural strength. The reliability index for standard PSSC composite bridge which is designed to satisfy the allowable stress for flexural strength are higher than 3.5 which is required reliability indexes on American code for LRFD. Reliability of PSSC girder which is designed based on allowable stress of bridge design code is high for flexural strength.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.18 no.3
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• pp.277-289
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• 2005

The study examines the limit strength for steel cable-stayed bridges. A case studies have been performed in order to evaluate the limit strength lot steel cable-stayed bridges using nonlinear inelastic analysis approach and bifurcation point instability analysis approach, effective tangent modulus $(E_f)$ method. To realize it, a practical nonlinear inelastic analysis condoling the initial shape is developed. In the initial shape analysis, updated structural configuration is introduced instead of initial member forces for beam-column members at every iterative step. Geometric and material nonlinearities of beam-column members are accounted by using stability function, and by using CRC tangent modulus and parabolic function, respectively Besides, geometric nonlinearity of cable members is accounted by using secant value of equivalent modulus of elasticity. The load-displacement relationships obtained by the proposed method are compared well with those given by other approaches. The limit strengths evaluated by the proposed nonlinear inelastic analysis for the proposed cable-stayed bridges with tee dimensional configuration compared with those by the inelastic bifurcation point instability analyses.

• Journal of the Korean Society of Industry Convergence
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• v.25 no.6_2
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• pp.987-992
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• 2022

STS 410, a representative martensitic stainless steel, contains 13 % chromium and is used for building materials, automobile parts, office equipment, kitchen utensils, and tableware. In general, the strength of STS 410 changes by the carbon content, and STS 410 of low carbon has excellent toughness and high carbon has excellent abrasion resistance. In this study, a fatigue test was performed on the STS 410 material to evaluate the exact fatigue limit and to evaluate the behavior of the material against fatigue. In addition, the effect on burnishing, a kind of plastic processing that creates a smooth surface by pressing a ball or roller on the inner and outer surfaces of the material was evaluated. The fatigue limit was 509 MPa for the STS 410 material, and the result was 54.5 % of the tensile strength. The fatigue limit was 542 MPa for the specimen of diamind burnished STS 410 material, and it was 58.5 % of the tensile strength.

• Journal of the Korean Society of Industry Convergence
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• v.26 no.4_2
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• pp.585-589
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• 2023

Unlike general carbon steel, stainless steel's mechanical properties change depending on the content of chromium and nickel. In this study, since stainless steel for high-temperature pressure container parts is used as shafts, the fatigue strength and fatigue limit of the materials were evaluated using a rotational bending fatigue test. Meanwhile, fatigue analysis was conducted under the same conditions as the specimen for structural analysis and fatigue analysis of stainless steel for high-temperature pressure container parts. Using the fatigue analysis results, we tried to derive the life of the material and the safety factor for each part. As a result of performing a fatigue test by processing a specimen for the fatigue test of A182 F6A stainless steel, the fatigue limit was 548 MPa. The ratio between the tensile strength and fatigue limit of the material was 0.545, representing 54.5% of the tensile strength.

• Journal of the Earthquake Engineering Society of Korea
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• v.28 no.4
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• pp.223-231
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• 2024

For the OPR1000, a standard power plant in Korea, an analytical model of the containment building considering voids and deterioration was built with multilayer shell elements. Voids were placed in the vulnerable parts of the analysis model, and the deterioration effects of concrete and rebar were reflected in the material model. To check the impact of voids and deterioration on the seismic performance of the containment building, iterative push-over analysis was performed on four cases of the analytical model with and without voids and deterioration. It was found that the effect of voids with a volume ratio of 0.6% on the seismic performance of the containment building was insignificant. The effect of strength reduction and cross-sectional area loss of reinforcement due to deterioration and the impact of strength increase of concrete due to long-term hardening offset each other, resulting in a slight increase in the lateral resistance of the containment building. To determine the limit state that adequately represents the seismic performance of the containment building considering voids and deterioration, the Ogaki shear strength equation, ASCE 43-05 low shear wall allowable lateral displacement ratio, and JEAC 4601 shear strain limit were compared and examined with the analytically derived failure point (ultimate point) in this study.

• Journal of Industrial Technology
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• v.19
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• pp.75-79
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• 1999

Rotary bending fatigue tests were performed to investigate the effects of 2-phase matrix structure on fatigue limit with prepared specimens in high strength ductile irons. Two types of the specimens with different microstructures have been used. Series A has sorbite and series B has bainite. Fatigue limits of both specimens are improved comparing with as cast specimen. The fatigue limit is higher in series B than in series A. The reason why the fatigue limit of series A shows inferiority to that of series B is due to the transition of micro fatigue cracks to mesocrack occurs very rapidly, so increased stress intensity factor drives the fatigue crack growth. The higher fatigue limit of series B which has bainite is caused by the ${\gamma}$ layer contained in microstructure impede the rapid growth of micro fatigue crack to mesocrack and ${\alpha}$ layer around graphite has the higher capacity for the absorption of plastic deformation energy than sorbite.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.759-764
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• 1997

In this study, Fatigue behavior of laser weldment in heterogeneous materials was investigated. Fatigue strength test and fatigue crack propagation test were performed for specimens with laser weldment in heterogeneous materials, and hardness test was performed. From the fatigue strength test. it was observed that the difference of strength between heterogeneous materials had eflect on crack initiation position and fatigue limit. From the fatigue crack propagation test. it was observed that fatigue behavior of laser weldment in heterogeneous materials is different from that in same materials. The difference of strength between heterogeneous materials and laser weldment had effect on fatigue crack propagation rate.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.6
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• pp.235-244
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• 2021

This study analyzes the applicability of limit state design method on bridge evaluation by considering the experiment of the existing bridge. The test strength of the member is obtained from the PSC beam bridge experiment. The test strength is compared with the calculated strength obtained from the statistical characteristics of material test strength and the two values are almost the same. The response modification factor and dynamic impact factor are obtained from the vehicle loading test. The rating factor is calculated by applying limit state design method as well as current evaluation method and the results are compared. The reliability index of the test bridge is calculated by using the statistical properties of the member strength obtained from material test and simulation. When the statistical properties of the PSC beam tested in this study are applied, the reliability index with a larger value was obtained than the reliability index obtained with the statistical properties of the design code.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.4
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• pp.449-457
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• 2023

In this study, the structural limit for concrete was experimentally determined against corrosion of steel. The structural limit was taken as (1) the deformation of concrete at yielding, (2) the maximum pull-out strength and (3) the pull-out strength at the level for uncorroded specimen. Corrosion of steel was accelerated by extracting charges from steel surface to govern degree of steel corrosion. As a result, an increase in the steel diameter resulted in an increase in the corrosion degree to reach the concrete deformation at yielding. Again, an increase in the steel diameter resulted in an increase in the extracted charge to meet the maximum and uncorroded-equivalent level for the bond strength. However, the mass loss was marginally affected by the steel size, reflecting that these parameters could be used to alert the structural limit.

• Geomechanics and Engineering
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• v.29 no.4
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• pp.421-434
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• 2022

In the present study, reference samples were prepared using ore preparation facility tailings taken from the copper mine (Kure, Kastamonu), Portland cement (PC) in certain proportions (3 wt%, 5 wt%, 7 wt%, 9wt% and 11 wt%), and water. Then natural zeolite taken from the Bigadic Region was mixed in certain proportions (10 wt%, 20 wt%, 30 wt% and 40 wt%) for each cement ratio, instead of the PC, to prepare zeolite-substituted CPB samples. Thus, the effect of using Zeolite instead of PC on CPB's strength was investigated. The obtained CPB samples were kept in the curing cabinet at a temperature of 25℃ and at least 80% humidity, and they were subjected to the Uniaxial Compressive Strength (UCS) test at the end of the curing periods of 3, 7, 14, 28, 56, and 90 days. Except for the 3 wt% cement ratio, zeolite substitution was observed to increase the compressive strength in all mixtures. Also, the liquefaction risk limit for paste backfill was achieved for all mixtures, and the desired strength limit value (0.7 MPa) was achieved for all mixtures with 28 days of curing time and 7 wt%, 9 wt%, 11 wt% cement ratios and 5% cement - 10% zeolite substituted mixture. Moreover, the limit value (4 MPa) required for use as roof support was obtained only for mixtures with 11% cement - 10% and 20% zeolite content. Generally, zeolite substitution seems to be more effective in early strength (up to 28th day). It has been determined that the long-term strength losses of zeolite-substituted paste backfill mixtures were caused by the reaction of sulfate and hydration products to form secondary gypsum, ettringite, and iron sulfate.